The following patents show the state of the art for reversible umbrellas as known to applicants:
U.S. Pat. No. 428,661 issued May 27, 1890 to Albin for UMBRELLA OR PARASOL FRAME;
U.S. Pat. No. 2,607,362 issued Aug. 19, 1952 to Evans for REVERSIBLE UMBRELLA;
U.S. Pat. No. 2,725,066 issued Nov. 29, 1955 to Estes et al. for REVERSIBLE UMBRELLA;
U.S. Pat. No. 2,788,792 issued Apr. 16, 1957 to Koller for WIND-RESISTANT REVERSIBLE UMBRELLA; and
U.S. Pat. No. 5,284,172 issued Feb. 8, 1994 to Teate, Jr. for REVERSING UMBRELLA APPARATUS.
Albin, Evans and Koller show reversible umbrellas supported on shafts of constant lengths.
Estes discloses several embodiments. The embodiment of FIGS. 1-3has a circular cover supported beneath ribs on a constant-length shaft.
The embodiment of FIGS. 4-7 has a circular flexible cover supported on braces connected to telescopic ribs on a constant-length shaft. The braces are also connected to a reciprocable hand-hold that is manipulated on the shaft to open the umbrella and close it with the cover turned inside out.
The embodiment of FIG. 8 in Estes has a square cover on a constant-length shaft. The square cover is turned inside out by ribs and braces externally of the cover as the umbrella is closed.
Estes' embodiment of FIGS. 9-14 has a circular cover supported on telescopic ribs extending radially from a reciprocable hand-hold on a telescopic shaft and on braces extending radially from a cap on top of the telescopic shaft. The cover is turned inside out as the umbrella is closed. The telescopic ribs undesirably increase the weight of the umbrella.
Teate discloses an umbrella with a tubular shaft including a collar with ribs mounted to the collar and each rib including a slide housing and a support rib. A cover is secured to the ribs. The slide is arranged in cooperation with the slide housings to reverse the arcuate orientation of the ribs and turn the ribs from a downward to an upward position.
An umbrella with a square cover has the advantage of stability, as noted by Estes, and also has the advantage of providing more protection in confined areas, as in getting in and out of a car. The advantages of umbrellas with telescopic shafts that shorten when the umbrella is closed are well known but most such umbrellas do not turn the cover inside out as the umbrella is closed.